Bugfix change from function to macro

This change is similar to commit 89be4e14: After find_package_append_to
changed from function to macro to pick up the configuration not only
from the module itself but also from everything it pulled it, the
variable MODULE is overwritten (variable module in lower case is a
parameter, so it is replaced in the source body). Thus, the test in the
end is not whether *this* module was found, but if its last dependency
was! This made the build crash only in some projects but not in others.
Merge pull request #205 from rolk/205_tinyxml

Dependent packages fail if opm-core uses embedded TinyXML
Use 1e-8 as residual tolerance similar to istl. Added verbosity mode.
Added a fast amg version of AMG (with one step of Gaus-Seidel smoothing) and AMG with Krylov-cycle.

The former is only available when using the inofficial 2.2.1 cmake release.
The latter is currently not optimized.
Adapted the documentation.
Merge remote-tracking branch 'origin/release-dune-cmake' into release-dune-cmake